Machinable titanium base alloy containing arsenic



Patented Feb. 2, 1954 MAGHINABLE' TITANIUM BASE ALLOY CONTAINING ARSENIC Robert I. J-aflee, Worthington, Ohio, assignor, by

mesne assignments, to Kcnnecott Copper Corporation, New York, N. Y., a corporation of New York No Drawing. Application April 26, 1952, Serial No. 284,640

2, Claims. (Cl. 75-177) This invention relates to titanium-base alloys and, more particularly, to titanium-base alloys characterized by good' machining properties.

In the past, little has been known concerning the machinability of titanium metal and, consequently, there is practically no information relative to machinable alloys of titanium. Separate publications have compared the machinability of titanium to that of stainless steel, in one instance, and to that of free-machining stainless steel in another instance. Since the machinability of stainless steel and free-machining stainless steel differ by a factor of about two,

.it will be apparent that the actual machinability of titanium metal is a somewhat controversial subject. In view of recent interest in titanium alloys and their applications, it has become increasingly desirable that information relative to the machinability of titanium alloys be obtained and that titanium alloys having good machining properties be developed.

It is, therefore, an object of this invention to provide alloys of titanium which are readily machinable.

It is a further object of this invention to provide free-machining alloys of titanium comprising titanium and an element having low solubility in titanium.

Yet another object of this invention is to provide free-machining alloys comprising titanium and arsenic.

Other objects and advantages of this invention will be apparent, in view of the following detailed description thereof:

In general, this invention relates to free-machining titanium-base alloys comprising titanium and from about 0.05% to about 0.65% arsenic. A preferred range of compositions is from 0.1% to 0.6% arsenic, balance essentially all titanium.

Alloys of this invention may readily be prepared in an arc-melting process under an inert atmosphere. Water-cooled crucibles are desirable. Typically, the operation involves charging the crucible with a mixture of crushed, leached and dried titanium sponge and the arsenic metal. The crucible and charge are evacuated by vacuum pump to a pressure of about 100 microns and held there briefly. Hot water is circulated through the jacket (provided for water cooling) during the evacuation process to aid in outgas sing the crucible. Following evacuation, the crucible is flushed with argon. After this process has been repeated once or twice, the argon flow is adjusted and regulated to give a positive pressure of 1 to 2 p. s. 1. Cold water is circulated 2 through the jacket. and the arc is. struck. To insure uniform, distribution, of the arsenic addition, it is sometimes desirable to machine the original ingot to chips, clean the chips, and remelt the chips according to the process describedabove.

Titanium-arsenic alloys; have been prepared and evaluated for machinability with results as tabulated in Table I below. Two common types of machining operations have been used in evaluating the machining properties of the present alloys. These two operations, turning on a lathe and cutting with a saw, are believed to be representative machining operations and to afford a reasonable evaluation of relative machinability. Data reported in Table I are reported on the basis of the machinability of unalloyed titanium as a reference. A value of 100 has arbitrarily been assigned as the machinability index of unalloyed titanium. Alloys which out faster, or which have heavier feeds, have an index rating greater than 100. The exact index value is conveniently computed from observed values obtained during lathe tests. For example, the

- lathe-test index may be computed from the average feed by an equation, as follows:

Avg. Feed on Alloy Avg. Feed on Standard TABLE I Machinability of Ti-As alloys Composition 1 Arsenic (Percent) gggf gg 1 Balance titanium.

made on an 11 ft.6 in. band saw, travelling at,

46 ft./min., and having A-in. Wide blade with 10 teeth per inch.

The increased machinability obtained by alloying titanium with arsenic isgained without significant loss of mechanical properties. Table II below shows that the mechanical properties of 1 titanium are generally maintained by the alloys of this invention:

TABLE II Mechanical properties of Ti-As alloys Ultimate 0.27 Elonga Reduc- Vickers gs gg i Tensile Yielfi tion, tion of Hardcexit As Strength, Strength, Percent Area, ness p. s. i. p. s. i. in 1-inch Percent Number Unalloyedu 75, 400 54, 300 29 51 183 0.26 72, 700 52, 600 28 50 172 0.51 l 71, 600 48, 100 29 63 180 0.67 93, 800 73, 500 24: 42 250 1 Balance titanium.

From Table 11 above, it is clear that the mechanical properties of titanium are not impaired by the alloying with it of arsenic. The Ti-As alloys of this invention have good strength and ductility, and retain the hardness of the uni -i purposes only. The titanium used in preparing the alloys of this invention may be prepared by either the magnesium-reduction method or by the iodide method and may contain small amounts of such impurities as carbon, iron, or nitrogen.

What is claimed is:

1. Titanium-base alloys consisting essentially from 0.05% to 0.65% arsenic, balance titanium and characterized by a machinability in excess of 100 as determined by a lathe test and as compared with a machinability of 100 for an unalloyed titanium specimen.

2. Titanium-base alloys consisting essentially from 0.1% to 0.6% arsenic, balance titanium and characterized by a machinability in excess of 100 as determined by a lathe test and as compared with a machinability of 100 for an unalloyed titanium specimen.

ROBERT I. J AFFEE.

References Cited in the file of this patent The Influence of Insoluble Phases on the Machinability of Titanium, by R. M. Goldhoii et a1. ASM Preprint No. 30 (1952). 

1. TITAMIUM-BASE ALLOYS CONSISTING ESSENTIALLY FROM 0.05% TO 0.65% ARSENIC, BALANCE TITANIUM AND CHARACTERIZED BY A MACHINABILITY IN EXCESS OF 100 AS DETERMINED BY A LATHE TEST AND AS COMPARED WITH A MACHINABILITY OF 100 FOR AN UNALLOYED TITANIUM SPECIMEN. 